356 lines
11 KiB
C
356 lines
11 KiB
C
/*
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* CDE - Common Desktop Environment
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*
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* Copyright (c) 1993-2012, The Open Group. All rights reserved.
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*
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* These libraries and programs are free software; you can
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* redistribute them and/or modify them under the terms of the GNU
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* Lesser General Public License as published by the Free Software
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* Foundation; either version 2 of the License, or (at your option)
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* any later version.
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*
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* These libraries and programs are distributed in the hope that
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* they will be useful, but WITHOUT ANY WARRANTY; without even the
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* implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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* PURPOSE. See the GNU Lesser General Public License for more
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* details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with these libraries and programs; if not, write
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* to the Free Software Foundation, Inc., 51 Franklin Street, Fifth
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* Floor, Boston, MA 02110-1301 USA
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*/
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/* $XConsortium: lzss.cc /main/5 1996/07/18 16:00:08 drk $ */
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#include "compression/lzss.h"
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/*
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Adapted from LDS (lossless datacompression sources) Version 1.1 by
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Nico E. de Vries.
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qfc. 12-8-93.
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*/
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/**************************************************************
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LZSS.C -- A Data Compression Program
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(tab = 4 spaces)
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***************************************************************
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4/6/1989 Haruhiko Okumura
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Use, distribute, and modify this program freely.
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Please send me your improved versions.
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PC-VAN SCIENCE
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NIFTY-Serve PAF01022
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CompuServe 74050,1022
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**************************************************************/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <ctype.h>
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#define N 4096 /* size of ring buffer */
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#define F 18 /* upper limit for match_length */
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#define THRESHOLD 2 /* encode string into position and length
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if match_length is greater than this */
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#define NIL N /* index for root of binary search trees */
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unsigned long int
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textsize = 0, /* text size counter */
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codesize = 0, /* code size counter */
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printcount = 0; /* counter for reporting progress every 1K bytes */
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unsigned char
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text_buf[N + F - 1]; /* ring buffer of size N,
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with extra F-1 bytes to facilitate string comparison */
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int match_position, match_length, /* of longest match. These are
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set by the InsertNode() procedure. */
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lson[N + 1], rson[N + 257], dad[N + 1]; /* left & right children &
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parents -- These constitute binary search trees. */
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//FILE *infile, *outfile; /* input & output files */
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void InitTree(void) /* initialize trees */
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{
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int i;
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/* For i = 0 to N - 1, rson[i] and lson[i] will be the right and
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left children of node i. These nodes need not be initialized.
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Also, dad[i] is the parent of node i. These are initialized to
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NIL (= N), which stands for 'not used.'
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For i = 0 to 255, rson[N + i + 1] is the root of the tree
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for strings that begin with character i. These are initialized
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to NIL. Note there are 256 trees. */
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for (i = N + 1; i <= N + 256; i++) rson[i] = NIL;
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for (i = 0; i < N; i++) dad[i] = NIL;
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}
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void InsertNode(int r)
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/* Inserts string of length F, text_buf[r..r+F-1], into one of the
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trees (text_buf[r]'th tree) and returns the longest-match position
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and length via the global variables match_position and match_length.
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If match_length = F, then removes the old node in favor of the new
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one, because the old one will be deleted sooner.
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Note r plays double role, as tree node and position in buffer. */
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{
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int i, p, cmp;
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unsigned char *key;
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cmp = 1; key = &text_buf[r]; p = N + 1 + key[0];
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rson[r] = lson[r] = NIL; match_length = 0;
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for ( ; ; ) {
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if (cmp >= 0) {
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if (rson[p] != NIL) p = rson[p];
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else { rson[p] = r; dad[r] = p; return; }
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} else {
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if (lson[p] != NIL) p = lson[p];
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else { lson[p] = r; dad[r] = p; return; }
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}
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for (i = 1; i < F; i++)
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if ((cmp = key[i] - text_buf[p + i]) != 0) break;
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if (i > match_length) {
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match_position = p;
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if ((match_length = i) >= F) break;
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}
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}
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dad[r] = dad[p]; lson[r] = lson[p]; rson[r] = rson[p];
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dad[lson[p]] = r; dad[rson[p]] = r;
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if (rson[dad[p]] == p) rson[dad[p]] = r;
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else lson[dad[p]] = r;
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dad[p] = NIL; /* remove p */
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}
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void DeleteNode(int p) /* deletes node p from tree */
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{
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int q;
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if (dad[p] == NIL) return; /* not in tree */
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if (rson[p] == NIL) q = lson[p];
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else if (lson[p] == NIL) q = rson[p];
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else {
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q = lson[p];
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if (rson[q] != NIL) {
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do { q = rson[q]; } while (rson[q] != NIL);
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rson[dad[q]] = lson[q]; dad[lson[q]] = dad[q];
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lson[q] = lson[p]; dad[lson[p]] = q;
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}
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rson[q] = rson[p]; dad[rson[p]] = q;
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}
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dad[q] = dad[p];
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if (rson[dad[p]] == p) rson[dad[p]] = q; else lson[dad[p]] = q;
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dad[p] = NIL;
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}
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void lzss::compress(const buffer& uncompressed, buffer& compressed)
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{
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if ( compressed.buf_sz() < uncompressed.buf_sz() )
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compressed.expand_chunk(uncompressed.buf_sz());
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////////////////////////////////////////////
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////////////////////////////////////////////
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int i, c, len, r, s, last_match_length, code_buf_ptr;
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unsigned char code_buf[17], mask;
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InitTree(); /* initialize trees */
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code_buf[0] = 0; /* code_buf[1..16] saves eight units of code, and
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code_buf[0] works as eight flags, "1" representing that the unit
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is an unencoded letter (1 byte), "0" a position-and-length pair
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(2 bytes). Thus, eight units require at most 16 bytes of code. */
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code_buf_ptr = mask = 1;
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s = 0; r = N - F;
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for (i = s; i < r; i++) text_buf[i] = ' '; /* Clear the buffer with
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any character that will appear often. */
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char* unc_str = uncompressed.get_base();
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int unc_str_len = uncompressed.content_sz();
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int unc_str_ptr = 0;
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for (len = 0; len < F; len++) {
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if ( unc_str_ptr == unc_str_len )
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break;
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c = unc_str[unc_str_ptr++];
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//cerr << char(c);
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text_buf[r + len] = c; /* Read F bytes into the last F bytes of
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the buffer */
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}
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if ((textsize = len) == 0) return; /* text of size zero */
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for (i = 1; i <= F; i++) InsertNode(r - i); /* Insert the F strings,
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each of which begins with one or more 'space' characters. Note
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the order in which these strings are inserted. This way,
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degenerate trees will be less likely to occur. */
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InsertNode(r); /* Finally, insert the whole string just read. The
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global variables match_length and match_position are set. */
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do {
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if (match_length > len) match_length = len; /* match_length
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may be spuriously long near the end of text. */
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if (match_length <= THRESHOLD) {
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match_length = 1; /* Not long enough match. Send one byte. */
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code_buf[0] |= mask; /* 'send one byte' flag */
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code_buf[code_buf_ptr++] = text_buf[r]; /* Send uncoded. */
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} else {
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code_buf[code_buf_ptr++] = (unsigned char) match_position;
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code_buf[code_buf_ptr++] = (unsigned char)
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(((match_position >> 4) & 0xf0)
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| (match_length - (THRESHOLD + 1))); /* Send position and
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length pair. Note match_length > THRESHOLD. */
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}
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if ((mask <<= 1) == 0) { /* Shift mask left one bit. */
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// for (i = 0; i < code_buf_ptr; i++) { /* Send at most 8 units of */
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// putc(code_buf[i], outfile); /* code together */
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// }
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compressed.put((char*)code_buf, code_buf_ptr, true);
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codesize += code_buf_ptr;
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code_buf[0] = 0; code_buf_ptr = mask = 1;
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}
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last_match_length = match_length;
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for (i = 0; i < last_match_length; i++) {
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if ( unc_str_ptr == unc_str_len )
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break;
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c = unc_str[unc_str_ptr++];
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DeleteNode(s); /* Delete old strings and */
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text_buf[s] = c; /* read new bytes */
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if (s < F - 1) text_buf[s + N] = c; /* If the position is
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near the end of buffer, extend the buffer to make
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string comparison easier. */
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//s = (s + 1) & (N - 1); r = (r + 1) & (N - 1);
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s++; s &= (N - 1); r++; r &= (N - 1);
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/* Since this is a ring buffer, increment the position
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modulo N. */
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InsertNode(r); /* Register the string in text_buf[r..r+F-1] */
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}
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// if ((textsize += i) > printcount) {
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// printf("%12ld\r", textsize); printcount += 1024;
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// /* Reports progress each time the textsize exceeds
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// multiples of 1024. */
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// }
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while (i++ < last_match_length) {/* After the end of text, */
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DeleteNode(s); /* no need to read, but */
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//s = (s + 1) & (N - 1); r = (r + 1) & (N - 1);
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s++; s &= (N - 1); r++; r &= (N - 1);
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if (--len) InsertNode(r); /* buffer may not be empty. */
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}
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} while (len > 0); /* until length of string to be processed is zero */
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if (code_buf_ptr > 1) { /* Send remaining code. */
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// for (i = 0; i < code_buf_ptr; i++) {
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// //putc(code_buf[i], outfile);
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// compressed.put(code_buf[i], true);
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// }
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compressed.put((char*)code_buf, code_buf_ptr, true);
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codesize += code_buf_ptr;
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}
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//printf("In : %ld bytes\n", textsize); /* Encoding is done. */
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//printf("Out: %ld bytes\n", codesize);
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//printf("Out/In: %.3f\n", (double)codesize / textsize);
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}
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void lzss::decompress(buffer& compressed, buffer& uncompressed)
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{
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int i, j, k, r, c;
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unsigned int flags;
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for (i = 0; i < N - F; i++) text_buf[i] = ' ';
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r = N - F; flags = 0;
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for (;;) {
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if (((flags >>= 1) & 256) == 0) {
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// if ((c = getc(infile)) == EOF) break;
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if ( compressed.content_sz() == 0 )
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break;
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compressed.getusc(c);
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flags = c | 0xff00; /* uses higher byte cleverly */
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} /* to count eight */
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if (flags & 1) {
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//if ((c = getc(infile)) == EOF) break;
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//putc(c, outfile); text_buf[r++] = c; r &= (N - 1);
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if ( compressed.content_sz() == 0 )
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break;
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compressed.getusc(c);
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//debug(cerr, char(c));
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uncompressed.put(char(c), true); text_buf[r++] = c; r &= (N - 1);
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} else {
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//if ((i = getc(infile)) == EOF) break;
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//if ((j = getc(infile)) == EOF) break;
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if ( compressed.content_sz() == 0 )
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break;
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else {
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compressed.getusc(i);
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}
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if ( compressed.content_sz() == 0 )
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break;
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else
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compressed.getusc(j);
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i |= ((j & 0xf0) << 4); j = (j & 0x0f) + THRESHOLD;
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for (k = 0; k <= j; k++) {
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c = text_buf[(i + k) & (N - 1)];
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//putc(c, outfile);
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//debug(cerr, char(c));
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uncompressed.put(char(c), true);
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text_buf[r++] = c; r &= (N - 1);
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}
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}
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}
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}
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io_status lzss::build_dict(lex_func_t, getchar_func_t)
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{
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return done;
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}
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MMDB_BODIES(lzss)
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